Transfer conduit assembly for cryogenic liquid



April 28, 1964 G. c. HAETTINGER TRANSFER CONDUIT ASSEMBLY FOR CRYOGENIC LIQUID Filed May 2, 1961 INVENTOR. GEORGE C. HAETTINGER BY ATTOR/VEV United States Patent Office 3,136,555 Patented Apr. 28, 1964 3,130,555 TRANSFER CGNEEUIT ASSEMBLY FOR CRYQGENIC LIQ George Q. Haettinger, Indianapolis, Ind, assignor to Union 'Carhide Corporation, a corporation of New York Filed May 2, 1961, Ser. No. 107,170 Claims. (Cl. 6255) This invention relates to an apparatus for transferring low boiling liquefied gases and more particularly to transferring low boiling liquefied gases through a liquefied gas transfer conduit.

Heretofore, low boiling liquefied gases having atmospheric boiling points below about l00 C. such as oxygen, nitrogen, helium and hydrogen generally have required a high quality insulating system for their storage containers and transfer conduits in order to reduce losses due to evaporation. Insofar as transfer conduits were concerned, such insulating material was usually contained in an evacuated insulation space between two concentric conduits. While this insulating arrangement was satisfactory for storage containers and rigidly positioned transfer conduits, it was not so satisfactory where the utilization of a flexible transfer conduit was required. The requirement of two concentric conduits not only increased the weight and the bulk of the transfer conduit but also eliminated its employment in aircraft where design requirements stipulated that the transfer conduit must travel a tortuous path.

It is, therefore, an object of this invention to provide a flexible low boiling liquefied gas transfer conduit which does not require an external insulating material for protection against excessive product liquefied gas evaporation losses. A further object is to provide a flexible low boiling liquefied gas transfer conduit which is relatively light in weight and which has reduced bulk.

These and other objects of this invention will become apparent from the following description and the accompanying drawings embodying the invention in which:

FIG. 1 is a longitudinal cross-section through a low boiling liquefied gas transfer conduit assembly embodying features of the present invention.

FIG. 2 is a longitudinal cross-section through a low boiling liquefied gas transfer conduit assembly embodying further features of the present invention.

The present invention is made possible by the novel manner in which the well-known Leidenfrost phenomenon is employed. Heat transfer by conduction through an uninsulated section of a liquefied gas transfer conduit vaporizes a small portion of the liquefied gas passing therethrough during the transfer operation thereby surrounding a major portion of such product liquefied gas with a gaseous film. This gaseous film impedes the further conduction of heat from the atmosphere to the product liquefied gas. Consequently, the product liquefied gas passes through this uninsulated section of the transfer line with a minimum of added vaporization losses.

Previous attempts by the prior art to employ this concept of shielding the transferring product liquefied gas from ambient heat were only partially successful. This was due to the inability of such prior art to cope with the conflicting problems of permitting enough heat to pass through the uninsulated transfer conduit wall for proper internal vaporization and, at the same time, preventing this heat from being conducted beyond the uninsulated section of transfer conduit into the storage container or into the insulated section of the transfer conduit longitudinally adjacent to the uninsulated section. If the protective internal gaseous film is not maintained along the entire length of the uninsulated section, the product liquid will contact the Wall of the transfer conduit and result in prohibitive product losses due to excessive va porization of the product liquid.

These problems are most severe at the junction of the uninsulated section of the transfer conduit with the insulated section or with a storage container. If the uninsulated section is connected directly to the insulated section, i.e.if the uninsulated product liquefied gas con duit is directly attached to the insulated product liquefied gas conduit, the entrance of the uninsulated section will be too cold to properly maintain the protective gaseous film. Furthermore, any heat conducted from the uninsulated section directly into the insulated product liquid conduct would cause excessive vaporation therein. Such circumstances negate the advantage of employing the insulated section of the transfer conduit to reduce heat losses to the overall system.

The instant invention eliminates the problems arising from direct heat conduction from the uninsulated product liquid conduit by interposing, between the insulated and uninsulated section, a unique transition member. This transition member is connected to the outer periphery of a concentric conduit, surrounding the insulated product liquefied gas conduit, and to the uninsulated section of the transfer conduit. The insulated product liquefied gas conduit terminates adjacent to and in indirect thermalconductive relation with the uninsulated conduit. By the term indirect thermal-conductive relation, it is meant that the insulated and uninsulated sections of the product liquefied gas conduit are not in direct contiguous contact. Therefore, suificient ambient heat may be transferred along the uninsulated section up to, and including, the transition member to maintain the necessary gaseous film along the inner surface of the uninsulated conduit without being directly conducted into the insulated product liquefied gas conduit. The liquefied gas is conducted from the insulated conduit zone, through the transition zone and into the uninsulated conduit zone such that vaporization of a minor portion of such liquefied gas only occurs in the transition zone and the uninsulated conduit zone.

With particular reference being made to FIG. 1, the preferred embodiment of the invention, comprising a liquefied gas transfer line, includes a double-walled vacuum-insulated transfer line section 10, an uninsulated transfer line section 12, and a transition member 14 interposed therebetween.

Double-walled vacuum-insulated transfer line section 19 is formed by a first product liquid conduit 16, an outer shell 13 which concentrically surrounds conduit 16, and an evacuab e insulation space 29 therebetween. Such insulation space 20 is preferably substantially completely filled with an opacified insulating material. The term opacified insulation as used herein refers to a two component insulating system comprising a low heat conductive, radiation-permeable material and a radiant heat impervious material which is capable of reducing the passage of infrared radiation rays without significantly increasing the thermal conductivity of the insulating system. Also, the term radiant heat barrier as used herein refers to radiation opaque or radiant heat energy impervious materials which reduce the penetration of infrared heat rays through the insulating system either by radiant heat reflection radiant heat adsorption or both.

The opacified insulation may take the form of a low heat conductive material and a multiplicity of spaced radiation-impervious barriers. As more fully described and claimed in copending US. application Serial No;

597,947, filed July 16, 1956, now Patent No. 3,007,596, in the name of L. C. Matsch, the low heat conductive material may be fiber insulation which may be produced in sheet form. Examples include a filamentary glass material such as glass Wool and fiber glass, preferably having fiber diameters less than about 50 microns. Also such fibrous materials preferably have a fiber orientation substantially perpendicular to the direction of heat flow across the insulation space; The spaced radiation-impervious barriers may comprise either a metal, metal oxide, or metal coated material, such as aluminum coated plastic film or other radiation reflective or radiation adsorptive material or a suitable combination thereof. Radiation reflective material comprising thin metal foils are particularly suited in the practice of the present invention, for example, reflective sheets of aluminum foil having a thickness between 0.2 mm. and 0.002 mm. When fiber sheets are used as the low-conductive material, they may additionally serve as a support means for relatively fragile impervious sheets. For example, it is preferred that an aluminum foil-fiber sheet insulation be spirally wrapped around inner liquefied gas conduit 16 with one end of the insulation wrapping in contact with inner conduit 16, and the other end nearest outer shell to, or in actual contact therewith.

It will be appreciated that other forms of opacified insulation may be used. For example, the radiation impervious barriers may be incorporated directly into the low heat conductive material as described and claimed in US. Patent No. 2,967,152, issued in the name of L. C. Matsch et al. Such opacified powder-vacuum type might comprise, for example, equal parts by weight of copper flakes and finely divided silica. The latter material has a very low solid conductivity value but is quite transparent to radiation. The copper fiakes serve to markedly reduce the radiant heat inleak.

Even though the previously described preferred opacified insulation is more effective than straight vacuum insulation at higher internal pressure (poorer vacuum), its effective thermal insulation life is extended if the pressure can be maintained at or below a desired level such as, for example, below about 25 microns of mercury absolute. A gas removing material such as an adsorbent may be used in insulation space 2% to remove by adsorption any gas entering through the joints of the transfer line. In particular, crystalline zeolitic molecular sieves having pores of at least about 5 Angstrom units in size, as disclosed in US; Patent No. 2,900,800, issued in the name of P. E. Loveday, may be employed as the adsorbent in accordance with the teachings therein since they have extremely high adsorptive capacity at the temperature and pressure conditions existing in insulation space 20 and are chemically inert toward any gases which might leak into such insulating space. The adsorbent material may be provided within insulation space 20, for example, by blister 21 which is wrapped around conduit 16 or may be intermixed with the insulation material. If a blister is provided, a wire screen 21a may be employed to provide gas communication between insulation space 21) and the adsorbent material within blister 21.

Transition member 14, which is preferably constructed of a relatively high thermal-conductivity metal such as aluminum, is connected to the outer periphery of one end of outer shell 18 and also to the adjacent communicating end of the uninsulated product liquefied gas conduit 12. If conduit 12 has about the same diameter as conduit 16, as shown in FIG. 1, then transition member 14 includes a reducing section 22 such that outer shell 18 and conduit 12 may be integrally connected. Transition member 14 also connects conduit 16 with outer shell 18 by end section 24, thereby sealing the end of insulation space 29.

As shown, end section 24 is preferably attached to the respective ends of conduit 16 and outer shell 18 by reducing insulation space it in diameter. This permits an end section 24 of increased length thereby providing an increased heat inleak path, and also permits the utilization of the insulating material up to the end of conduit 16. Alternately, end section 24 may be attached to the outer surface of conduit 16 at a point away from the end of conduit 12, as depicted in FIG. 2. The exact placement of end section 24 in FIGS. 1 and 2 is not critical as long as it separa es insulation space 20 from the inleak of transition member 14. Conduit 16 preferably extends into the interior of transition member 14 and ends axially adjacent to conduit 12 but does not directly contact such conduit. By extending into the interior of transition member 14 the end of conduit 16 is provided in close indirect heat exchange relationship with conduit 12 thereby permitting such end to be substantially surrounded by the product liquefied gas within transition member 14.

As an example of the operation of this invention, consider that double-walled transfer line portion 10 is attached and rigidly positioned to a low boiling liquefied gas storage container and that a flexible, uninsulated transfer line portion 12 is connected to transfer line 10 by transition member 14. Conduit 12 may be constructed of any suitable material such as metal or solid organic polymer which is useful to maintain the Leidenfrost phenomenon.

In transferring the product liquid from the storage container, such liquefied gas passes through conduit 16 and into transition member 14 from which liquid passes into uninsulated conduit 12. Upon contacting the exterior walls of transition member 14 and uninsulated conduit 12, a minor portion of the product liquefied gas is vaporized by ambient heat which is conducted through the aforementioned walls. This gaseous film protects the remaining major portion of the product liquid from further excessive vaporization by impeding the further conduction of heat from the atmosphere to such major portion. Ambient heat is prevented from being directly conducted into conduit 16 since conduits 16 and 12 are adjacent to but not in direct contact with one another. Indirectly, ambient heat may be conducted to conduit 16 through end member 24.

The construction of end member 24 in FIG. 1 largely eliminates this problem of direct heat conduction in that any heat which is conducted through end member 24 will be substantially completely intercepted by the product liquefied gas in transition member 14. By increasing the length of transition member 14 to accommodate the end member 24 of FIG. 1, the increased heat transfer surface area of transition member 14- resulting therefrom, aids in conducting heat to the inlet of conduit 12 thereby insuring that there will be a gaseous film surrounding the major portion of the product liquid at that critical point.

While this invention has been described in general terms insofar as the low boiling liquefied gas is concerned, it is to be realized that this invention is particularly applicable for transferring such low boiling liquefied gases as liquid oxygen, nitrogen, helium and hydrogen, argon,

neon.

Although the preferred embodiment has been described in detail, it is contemplated that modifications of the apparatus may be made and that some features may be employed without others, all within the spirit and scope of the invention.

As an example of the present invention, apparatus similar to that shown in FIG. 1 was constructed having a inch diameter inner conduit 16, a /2 inch outer diameter shell 18, a 0.034 inch outer diameter end section 24 terminating about inch from the inlet end of a inch outer diameter uninsulated conduit 12. When refrigerating an infra-red cell with a total heat load of /2 watt, this apparatus required one half the liquid nitrogen supplied by conventional prior art apparatus wherein the bare line was directly attached to the liquefied gas supply conduit. The above apparatus dimensions are illustrative only since not one of the dimensions are considered critical. Theexact configuration of a transfer line may vary with its application and may be determined, for example, by liquefied gas flow rates, ambient temperature conditions, and shape of the supply conduit to which the transfer line is connected.

What is claimed is:

1. A low boiling liquefied gas transfer conduit assembly comprising a first liquefied gas conduit; an outer shell which circumferentially surrounds said first liquefied gas conduit so as to form an evacuable insulation space therebetween; a second atmospherically exposed liquefied gas conduit; a transition member which integrally connects said. outer shell to said second liquefied gas conduit such that the first and second liquefied gas conduits are longitudinally adjacent and in indirect thermal-conductive relation; and means for vacuum-sealing said evacuable insulation space.

2.. A low boiling liquefied gas transfer line according to claim 1 wherein said first liquefied gas conduit and said outer shell are connected by said vacuum-sealing means in a manner such that said first liquefied gas conduit extends longitudinally beyond such connection into the space defined by said transition member.

3. A low boiling liquefied gas transfer line according to claim 1 wherein said first liquefied gas conduit and said outer shell are connected at their respective ends by said vacuum-sealing means in a manner such that said first liquefied gas conduit extends into the space defined by said transition member.

4. A low boiling liquefied gas transfer line according to claim 1 wherein said evacuable insulation space is substantially completely filled with an opacified insulating material.

5. A low boiling liquefied gas transfer line according to claim 4 wherein said opacified insulating material com prises alternate layers of a low heat conductive, radiation permeable material and a radiant heat impervious material, and is spirally wrapped around said first liquefied gas conduit.

References Cited in the file of this patent UNITED STATES PATENTS 2,785,536 Hinckley Mar. 19, 1957 2,871,670 Huzel et al. Feb. 3, 1959 2,970,452 Beckman et al. Feb. 7, 1961 2,980,448 Holben Apr. 18, 1961 2,996,893 Goodenough et al Aug. 22, 1961 3,034,319 Chelton May 15, 1962 FOREIGN PATENTS 794,761 Great Britain May 7, 1958 

1. A LOW BOILING LIQUEFIED GAS TRANSFER CONDUIT ASSEMBLY COMPRISING A FIRST LIQUEFIED GAS CONDUIT; AN OUTER SHELL WHICH CIRCUMFERENTIALLY SURROUNDS SAID FIRST LIIQUEFIED GAS CONDUIT SO AS TO FORM AN EVACUABLE INSULATION SPACE THEREBETWEEN; A SECOND ATMOSPHERICALLY EXPOSED LIQUEFIED GAS CONDUIT; A TRANSITION MEMBER WHICH INTEGRALLY CONNECTS SAID OUTER SHELL TO SAID SECOND LIQUEFIED GAS CONDUIT SUCH THAT THE FIRST AND SECOND LIQUEFIED GAS CONDUITS ARE LONGITUDINALLY ADJACENT AND IN INDIRECT THERMAL-CONDUCTIVE RELATION; AND MEANS FOR VACUUM-SEALING SAID EVACUABLE INSULATION SPACE. 